Plan B is a massive dose of hormones, & it can really mess up you body. You could have erratic bleeding for a few weeks, until it settles down again. I did. It made me really depressed & hormonal, too. Everyone reacts differently, though.

As you had sex again, 48 hours after taking plan B, they won't guarantee you won't become pregnant. If you are worried about this, I would speak to your doctor ASAP.